Air flow control systems



puff-vu `luly 31, 1962 Filed Aug. 13, 1959 M. w. PATRICK 3,047,209

AIR FLOW CONTROL SYSTEMS 2 Sheets-Sheet 1 BY Qf/f ATTORNEY` July 31,1962 M. w. PATRICK 3,047,209

AIR FLOW CONTROL SYSTEMS Filed Aug. 13, 1959 2 Sheets-Sheet 2 5T- O 46 IA 5K 66 l| 64 ll l I I M68 46! 1'| I I In v T b rllllllllllllllllllllllINVENTOR /lf/MM/ /f/Irf/af BY Wwf@ ATTORNEY` This invention relates toair ow control systems and more particularly to systems for controllingthe amount of air delivered by the blower in a forced air domesticheating and cooling system.

One of the diiculties encountered in the operation of forced hot airsystems is the tendency of the system t deliver substantial volumes ofrelatively cold air to the space to be heated, particularly at the startof the blower cycle. Under such conditions the cold ail within the ductsystem and the plenum chamber is forced into the room of the dwellingthus causing cold drafts and often lowering the temperature of the room.Also in the interests of efficiency and to prevent overheating thefurnace room, the blower should not be stopped immediately upon thecessation of operation of the burner. Under these conditions a similaralthough not so severe effect is. produced since in most systems the aircontinues to be delivered at full volume despite a substantial drop inits temperature.

In recognition of these difliculties, it has been proposed to modulatethe flow of air to reduce the volume of air delivered by the blower whenthe blower is started and as it continues to deliver cooler air afterthe burner is shut of. One such proposal is described and claimed inUnited States Patent Re. 24,421. However it has been found that thisunit tends to lag the system with the result that the volume of air isunduly restricted during the starting cycle and excessive air ispermitted to flow while the blower continues to run after the burner hasbeen shut off. Also, transient conditions may result in partial flowrestriction even when the burner and blower have been operating atnormal temperature for some time.

It is accordingly the principal purpose and object of the presentinvention to provide improved systems for controlling the volume of airdelivered by a blower associated with a forced air heating system whicheffectively prevents the delivery of objectionable amounts of -cold airinto the room to be heated under all operating conditions.

It is also an object of the present invention to provide improvedcontrol systems for blowers which assure the delivery of the full ratedcapacity of the blower at all times when the blower is operatingnormally and delivering air at a temperature above a preselected minimumtemperature or during the cooling cycle.

It is .a further object of the present invention to provide improvedcontrol systems for blowers which are positive and reliable inoperation, which are of relatively simple construction and which may beinstalled readily in existing systems as well as in new equipment.

It is an additional object of the invention to provide improved systemsand apparatus for controlling the output of a blower associated with. acombined forced air heating and cooling unit which functions effectivelyduring both the heating and cooling cycles without the attention of theoperator.

In accomplishing these and' other objects there is provided atemperature sensitive element for positioning an air flow control vanein the discharge throat of a blower, a heater element to modulate theaction of the temperature sensitive element and` a novel control circuitfor regulating the operation of the heater element .automatically duringthe heating and cooling cycles, these. ele- -nited States VParana icements cooperating to produce an overall system efficiency not heretoforeobtainable.

Additional objects and advantages of the present invention will becomeapparent as the description proceeds in connection with the accompanyingdrawings in which:

FIGURE l is a side elevation of a blower incorporattrical circuitforming a part of the present invention;

FIGURES 4 and 5 are enlarged fragmentary elevations of the apparatusshown in FIGURES l and 2, respectively;

FGURE 6 is a fragmentary elevation of the heater element forming a partof the present invention; and y FIGURE 7 is a fragmentary section takenalong line '7 7 of FIGURE 6.

Referringnow more particularly to the drawings, the blower assemblyindicated generally at 20 is of theV centrifugal type and is providedwith a rotor 22 which draws air in through inlet openings 24 in the sidewalls 26 and 23 of the blower housing and discharges it through the'throat 3d.

In .accordance with conventional practice, the blower assembly 20 willbe mounted in the fan compartment of a furnace with the inlet openings2d connected to the cold air return ducts and the discharge throat 30directing air over `the heat exchanger and thence through supply ductsto the rooms or other spaces to be heated. Since this arrangement isentirely conventional, the furnace heat exchanger, plenum chamber andassociated ducts have been omitted. However for further details of atypical installation, reference may be had lto Reissue Patent 24,421issued January 28, 1958, for Blower Discharge Volume Control.

When the system is adapted for cooling, the evaporator coils will beplaced in the furnace plenum chamber in accordance with conventionalpractice.

The blower rotor 22 is `driven at a constant speed by an electric motor32, preferably by a belt drive 34. The output of the blower iscontrolled by a restrictor vane assembly indicated generally at 36 whichis preferably of the same construction as that shown in aforesaidReissue Patent 124,421. The restrictor vane 36 is non-rotatably securedto a pivot shaft 38 rotatably mounted in the opposite side walls 26 and28 of the blower housing. One end of the Vane pivot shaft 38 projectsoutwardly beyond the blower side wall 26 into a box-like housing 40detachably secured to the side wall 26. Adjustably secured by bolts 42to a side wall 44 of the housing lil is one end of a coiled bi-metallicspring 46. The flattened opposite end 43 of the spring 46 extendsthrough a slot in the pro-` jecting portion of the Vane pivot shaft 38.The vbi-metallic spring 46 is so arranged that when it is heated it iseffective to move the vane 36 in a counterclockwise direction as viewedin FIGURE 4 to dispose the vane in the position shown in FIGURE 4 whereit permits substantially unrestricted flow of air through thedischarge'throat 3i) of the blower. When the spring 46 is cooled, it iseffective to move the vane in the opposite direction to the positionshown in FIGURE l, its movement in this direction being limited by.contact of an adjustable stop member Sil with the blower housing.

As more fully explained in the aforesaid Reissue Patent 24,421, the vaneassembly 36, because of its position in the discharge throat 30 of theblower, is capable of reducing the output of the blower to a fraction ofthefull blower capacity.

A strip heater assembly indicated generally at l52 is disposed in closesurface contact with substantially theentire length of the bi-metallicspring 46. As shown in FIGURES 6 and 7, the strip heater assemblyocmprises a length of wire 54 such as Chromel-A resistance wire encasedin a wrapping of berglass tape 56. The ends of the envelope formed bythe tape 56 are closed and reinforced by a fiberglass wrapping 58. Thefiberglass tape 56 is preferably provided with a silicon thermo-settingadhesive to permit its rapid, easy and permanent attachment to thesurface of the bi-metallic spring 46.

Mounted on the side Wall 6l) of the casing member 40 is a micro-switch62 which is normally closed and is opened when an actuating button 64 onits upper surface is slightly depressed. A switch actuator 66 isnon-rotatably secured to the projecting portion of the vane pivot arm 33and is provided with an arm 68 which is operative to depress lthe switchbutton 64 when the restrictor vane 36 is in its fully open position asshown in FIGURE 4.

The energization of the strip heater asembly 52 is controlled by `thecircuit which is shown in simplified form in FIGURE 3, to which detailedreference will now be be made. The blower motor 32 is connected to 1'10v. leads 70 and 72 through a conventional thermostatic switch 74. Inaccordance with conventional practice, the switch 74 is mounted on thefurnace plenum chamber and is set to close when the temperature of theair in the plenum chamber rises to a predetermined value, for example110" to 120 F. The burner control apparatus indicated generally at 76 isconnected to 24 v. circuit leads 78 and 80 through a two-waythermostatic switch 82 mounted in the space served by the furnace. Thus,when the temperature of the room or other space to be heated falls belowa pre-set level, the switch 82 closes, starting the burner which, aftera relatively short period of time, raises the temperature in the furnaceplenum chamber to a level which closes the thermostatic switch 74 andthe blower begins to operate.

When the blower first begins to operate, the air in the duct systembetween the furnace and the space to be heated is cold. If this air isforced rapidly into the room, it produces unpleasant cold drafts. It isfor this reason that the restrictor vane 36 occupies its position ofmaximum flow restriction when the blower begins tol operate. The rate atwhich the cold air is forced into the room is greatly reduced and theobjectionable drafts are substantially eliminated. However it is alsoimportant to remove the restriction from the throat of the blower assoon as possible to permit delivery of the full rated capacity of theblower as soon as the cold air is exhausted from the duct system and itis for this purpose that the unique combination of the bi-metallic strip46, the strip heater 52 and the associated control is provided.

With continuing reference to FIGURE 3, the strip heater 52 is controlledby the thermostatic switch 74, the micro-switch 62, and a normally openrelay switch 84 which is closed whenever the burner circuit is actautedupon closure of the thermostatic switch S2. Since switch 62 is normallyclosed, the strip heater 52 will be energized immediately when thethermostatic switch 74 closes after the burner has begun to operate.Accordingly when the blower begins to operate, the strip heater 52 isenergized and the ibimetal strip 46 immediately begins to move the vane36 from its initial full restricting position thus gradually increasingthe air flow delivered by the blower. This air ow change is gradual andthus the air temperature at the room diffusers is heldrelativelyconstant while the discharge velocity increases. When the roomthermostat 82 is satisfied, the burner control 76 s de-energized and therelay contacts 84 are allowed to open thus deenergizing the strip heater52.

However the blower 32 continues to run as long as the thermostaticswitch 74 is closed, that is as long as the temperature in the plenumchamber is above the off setting. During this time the bi-metallic strip46 cools and gradually closes the vane 36 and 4thus modulates the airflow from a maximum at the end of the `furnace cycle to a minimum at theend of the blower cycle.

When the system is adapted for cooling as well as heating the compressormotor 86 is switched on and oi by a normally open relay 88 in a 220 v.circuit 90. A second normally open relay 92 having contacts 93 and 94 inthe circuit for the heater 52 and the blower motor 32, respectively, inconnected in parallel with relay 84 and switch 74, respectively. Thuswhen thermostat 82 is closed in the cool position, the compressor motor86, the strip heater 52 and the blower motor 32 will be energizedsimultaneously.

When either the combustion device or the compressor is operating, .thestrip heater `52 is supplied with pulses of power just sufficient tomaintain it in the full open position. This is accomplished by the useof the switch actuator 68 which in the full open position of the vanedepresses the button 64 in the microswitch 62 thus opening the switch,momentarily breaking the circuit to the strip heater. The slight coolingof the bi-metal spring 46 retracts the actuator 63 slightly thuspermitting the microswitch 62 to close and again applying power to thestrip heater 52 thus maintaining the bi-metallic strip in relatively thesame position and without an excessive amount of stored heat. Thus boththe danger of overheating of the bi-metallic strip and waste of anexcessive amount of power is avoided by the provision and utiliza-tionof the switch 62.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiment is therefore to be considered in all respects as illustrativeand not restrictive, the scope of the invention being indicated by theappended claims rather than by the foregoing description, and allchanges which come wtihin the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersIPatent is:

l. Apparatus for regulating the output of a forced hot air heatingsystem comprising a blower for delivering warm air to the space to beheated, a vane pivotally mounted in the discharge throat of said blowerfor movement betwen a flow restricting position and a non-restirctingposition, a bi-metallic coil spring having one end rigid with saidblower and the other end operably connected to said vane and arranged tomove said vane toward said non-restricting position when said spring isheated and to move said vane to said restricting position when saidspring is cooled, a heater element for selectively heating said spring,and means for energizing said heater element when said blower isinitially energized.

2. The combination according to claim l wherein said heater elementcomprises a strip heater in close surface contact with said bi-metallicspring.

3. Apparatus for regulating the output of a forced hot air heatingsystem comprising a blower for delivering warm air to the space to beheated, a vane pivotally mounted in the discharge throat of said blowerfor movement between a flow restricting position and a non-restrictingposition., a temperature sensitive element operably connected to saidvane and arranged to move said vane toward said non-restricting positionwhen said element is heated and to move said vane to said ow restrictingposition when said element is cooled, a heater element for selectivelyheating said temperature sensitive element, means for energizing saidheater element when said blower is initially energized, and means totemporarily de-energize said heater element when said vane reaches saidnonrestricting position.

4. Apparatus for regulating the output of a forced hot air heatingsystem comprising a blower for delivering air to the space to be heated,a vane pivotally mounted in the discharge throat -of said blower formovement between a flow restricting position and a non-restrictingposition, a temperature sensitive element operably connected to saidvane and arranged to move said vane toward said non-restricting positionwhen said element is heated and to move said vane to said flowrestricting position when said element is cooled, a heater element forselectively heating said temperature sensitive element, an electricalcircuit for energizing said heater element when said blower is initiallyenergized, a normally closed switch in said electrical circuit, andmeans responsive to movement of said vane to said non-restrictingposition to open said switch and temporarily cle-energize said heater.

5. Apparatus for regulating the output of a forced hot air heatingsystem comprising a blower for delivering =air to the space to beheated, a vane pivotally mounted in the discharge throat of said blowerfor movement between a How restricting position and a non-restrictingposition, a coiled bi-metallic spring having one end rigid with theblower and the Iopposite end operably connected to said vane andarranged to move said vane toward said nonrestricting position when saidelement is heated and to move said vane toward said ow restrictingposition when said element is cooled, a strip heater coi-led in closesurface contact with at least a portion of said loi-metallic spring, anelectrical circuit `for selectively energizing said strip heater, anormally closed switch in said circuit and a switch operator carried bysaid vane and operable to open said switch to temporarily de-energizesaid heater when said vane reaches said non-restricted position.

6. Apparatus for regulating the output of a forced air system forheating or cooling a space comprising a blower for delivering air tosaid space, a vane pivotally mounted in the discharge throat of said-blower for movement be-v i tween a ilow restricting position and anon-restricting i position when said element is cooled, a heater elementfor selectively heating said temperature sensitive element, `and meansfor energizing said heater element when said blower is initiallyenergized.

References Cited in the tile of this patent UNITED STATES PATENTSRe.24,421 Patrick Jan. 28, 1958 2,292,082 Miller Aug. 4, 1942 v2,385,096zMcCollum Sept. 18,1945 2,413,150 McReynolds Dec. 24, 1946 2,428,751Foulds Oct. 7, 1947 2,537,121 Copping Ian. 9, 1951 2,686,661 Gillick etal Aug. 17, 1954 2,693,914 v Payne Nov. 9, 1954 2,721,704 Patrick 06h25,1955 2,751,152 Ellenberlger June 19, 1956 2,769,312 Harrold et al Nov.6, 1956 2,793,811 Caselman May '28, 1957 2,865,610 Sparrow Dec. 23, 19582,905,790 Markham Sept. 22, 1959

